<!DOCTYPE html>
<style id="a">
    @namespace my_namespace_1 url("http://www.w3.org/1999/xhtml");
    @import url("nonexist.css");
</style>
<style id="b">
    div {
        color: green;
    }
</style>
<script src="../include.js"></script>
<script>
    test(() => {
        try {
            a.sheet.insertRule('@namespace my_namespace_3 url("http://www.w3.org/1999/xhtml")', 0);
            println("Can insert namespace rule into sheet with only @namespace and @import rules: PASS");
        } catch {
            println("Can insert namespace rule into sheet with only @namespace and @import rules: FAIL");
        }

        try {
            s.sheet.insertRule('@namespace my_namespace_3 url("http://www.w3.org/1999/xhtml")', 0);
            println("Cannot insert namespace rule into sheet with existing rules: FAIL");
        } catch {
            println("Cannot insert namespace rule into sheet with existing rules: PASS");
        }
    });
</script>